As prosecutors prepare to file murder charges against a Marine veteran in the stabbing of four homeless men, it has emerged that Itzcoati Ocampo was once a caring, charitable man until the horrors of Iraq 'killed the person he was'.

The 23-year-old was arrested on Friday after being chased down by a group of bystanders following the brutal stabbing of Vietnam veteran John Berry outside an Orange County fast food restaurant - the fourth vicious stabbing in as many weeks.

As Ocampo is held on psychological watch at the Orange County jail in Santa Ana, his family and friends have revealed the ex-Marine was once a caring man who helped the very people he is accused of murdering.

'I saw him so many times giving the last money he had in his pocket ... to the homeless, to the people that (are) asking for some help. ... My son's always been a role model,' his father Refugio Ocampo said in a video interview posted on Orange County Register website.

His son is now accused in
the stabbing deaths of James Patrick
McGillivray, 53, who was killed in Placentia on December 20, Lloyd
Middaugh,
42, who was found in Anaheim on December 28, Paulus Smit, 57, who was
found in Yorba Linda two days later and recently John Berry, 64, who was
stabbed to death in Anaheim on Friday.

It was only when he returned from serving in Iraq - where he was assigned to meet and inspect the wounded when they were flown in from combat zones en
route to the hospital - that he starting showing a darker side, became paranoid and delusional and struggled to find his way as a civilian.

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Worried: Refugio Ocampo, the father of the 23-year-old who is the prime suspect in the killings, is himself homeless and said the Iraq war killed the man his son used to be

Service: A relative holds a photograph of Itzcoatl posing proudly in his Marines uniform. He was said to have become paranoid and delusional after his deployment

Photos of homeless men killed in Orange County are displayed during a news conference in Santa Ana today as the DA file murder charges against former Marine Itzcoati Ocampo

Ocampo's father Refugio Ocampo, 49, said his son was a changed man after his deployment to the war zone in 2008.

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'They killed the person he was. And that's the only possibility I can think of that he would do something like that.'

His brother Mixcoatl Ocampo, 17, told the LA Times his brother sank into a depression and often suffered from hallucinations.

He said: 'He was always paranoid. He would search the closet and bathrooms of the home for
bombs. I would tell him to stop being crazy.'

The teen also revealed his brother had been applying for jobs everywhere but would never get hired and soon stopped even trying.

His father said things turned even worse when a close friend of his from the Marines died in Afghanistan in 2010.

'Once he received the news he was never the same. He said terrible things are going to
happen. The end of the world is coming. He started searching for hidden
things that weren't there, like guns and knives,' his father, 49, said.

Normal young man: Itzcoatl Ocampo's family have released these images of the young man, showing him in happier times

The victims: From left, James McGillivray was stabbed outside a shopping centre on December 20; Lloyd Middaugh was found stabbed on a riverbed on December 28; and Paulus Cornelius Smit was found stabbed outside a library on December 30

Locations: Police in Orange County, California said a serial killer was responsible for the first
three killings in December. They are investigating if the fourth, which happened on Friday, is connected

Cautious: Homeless people in Orange County were put on alert by police and advocates concerned that they're the target of a serial killer who has already slain three homeless men

Like the men his son is accused of preying
on, Mr Ocampo is homeless after losing his job as a warehouse manager.

He ended up living
under a bridge before finding shelter in the cab of a broken-down truck
he is helping repair.

Just days before he was arrested, Itzcoatl Ocampo visited his father,
warning him of the danger of being on the streets and showing him a
picture of one of the victims.

'He came back totally changed. It was almost like he didn't care anymore. He'd get fidgety, he'd
start shaking, spacing out. You'd see him staring off'

Anaheim Police Chief John Welter has
said investigators are confident they have the man responsible for the
murders. They are expected to hold a press conference later today.

Ocampo lived with his mother and
other relatives in the suburbs. His mother, who speaks little English,
tearfully brought her son's Marine Corps dress uniform out of a closet
and showed photos, citations and medals from his military service.

The son followed a friend into the
Marine Corps right out of high school in 2006 instead of going to
college as his father had hoped.

His family described a physical
condition Itzcoatl suffered in which his hands shook and he suffered
headaches. Medical treatments helped until he started drinking heavily,
they said.

A neighbour who is a Vietnam veteran
he and Ocampo's father both tried to push the 23-year-old to get
treatment at a veteran's hospital, but he refused.

Shrine: Several people pay their respects at a makeshift memorial site where a homeless man was killed in Anaheim, California last week

Clues: An image from surveillance video at a California strip mall shows James McGillivray before his death

All of the victims died as a result
of frenzied and brutal stabbings, with each man suffering at least 40
lacerations to their body.

'He would wake up screaming at the top of his lungs at least twice a week. He would have flashbacks'

Police hunted the serial killer for
weeks as he continued to prey on the destitute and needy, leaving the
entire homeless community in state of fear. Police have yet to
establish a motive for the senseless killings.

Fellow Marine Robert Hays,who met
Ocampo at basic training in San Diego in 2006, told the Los Angeles
Times he thought the 23-year-old was 'motivated and gung-ho'.

But he admits he noticed a vast change in him after his deployment.

He told the paper: 'He came back totally changed. It was almost like he didn't care anymore. He'd get fidgety, he'd
start shaking, spacing out. You'd see him staring off.'

Jesus Balbuena, who was Ocampo's roommate at
Camp Pendleton after his return from Iraq, said he would 'wake
up screaming at the top of his lungs twice a week. He would have
flashbacks' and would often weep as he talked about his family's demise into financial hardship.

When he left active duty in 2010 he
was devastated to find that his father - who studied law in Mexico - was
homeless and living under a bridge.

In custody: FBI special agent in charge William O'Leary speaks at the podium to announce the arrest of Itzcoatl Ocampo, who was charged with the murders of the four men on Tuesday

The Veterans Administration had diagnosed him with psychological problems.

Bonnie Tisdale, who acted as Ocampo's
supervisor at Camp Pendleton, told the Times he was a punctual and reliable
Marine.

'Regardless of what he's been accused of, I trust him with my
life,' the 27-year-old, of Vista, said. 'He's a veteran who did not get the
help he needed.

'It's traumatising over there and it
is difficult for Marines to come and ask for psychological help. Whether
he's proven innocent or guilty, he is our brother. We are his family.'

Mr Ocampo said he has repeatedly attempted to visit his son at the Orange County jail but has been turned away. '

They won't let us see him, even though the whole world is against him.'

He also said investigators
came to him on Friday night and showed him surveillance photos from a
crime scene, but he did not recognize his son as the person in the
images.

'If he did it, it wasn't right, obviously. But there's something wrong with him,' he said.

A community remembers: Megan Munoz, 13, adds a message to a spontaneous memorial to John Berry, on the spot where the homeless veteran was murdered behind a Carl's Jr. restaurant in Anaheim

Staying informed: Julia Adams, right, and Megan Munoz, both 13, read an article about the killings

While Refugio Ocampo lives away from
his family, they remain close. He saw his children every day, and his
wife brings food to the parking lot where the truck is located in the
city of Fullerton. He and his two sons went to get haircuts together
just a day before the arrest, the father said.

Refugio Ocampo, who said he was
educated as a lawyer in Mexico, immigrated with his wife and Itzcoatl in
1988 and became a U.S. citizen. He described building a successful life
in which he became a warehouse manager and bought a home in Yorba
Linda. In the past few years he lost his job, ran out of savings, lost
his house and separated from his wife.

Standing near the truck where he
sleeps, the father fought back tears as he described the changes he saw
in his son in the year since returning home.

'Before, he had the initiative to do things, the desire. But after the military, he didn't have any of that,' he said.

That was far from the son who in high school was a polite and motivated student, he said.

A school friend, Brian Doyle,
portrayed Itzcoatl Ocampo as a fun-loving teen who liked to hit on girls
when he joined the military. After he was discharged and returned home
he became isolated and trusted no one, said Doyle, 23.

Doyle had difficulty describing the change he saw in his friend from high school.

'He went from being a tall, geeky kid, really fun-loving...,' he said, trailing off.

Doyle said he once offered his friend
a self-help book based on Eastern philosophy that he had found useful
but Itzcoatl Ocampo rejected it.

Search: Police in Los Angeles, California arrested Ocampo in connection with the murder of a homeless man on Friday night. Witnesses chased the suspect as he fled a car park and led police to him